This review paper focus on Wireless Ad Hoc networks where I took review of its types, applications and security goals. A wireless ad hoc network is a decentralized type of wireless network. Mobile Ad Hoc Network Types of MANET Mobile Ad Hoc Networks are further classified. PDF | 3+ hours read | Principles of Ad Hoc Networking presents a systematic introduction to the fundamentals of ad hoc networks. An ad-hoc. Introduction to Ad hoc Networks. CS Advanced Topics in Wireless Networks. Drs. Baruch Awerbuch & Amitabh Mishra. Department of Computer Science.
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Differences to other Wireless. Networks. Wireless LAN. Ad hoc network. Bluetooth/ Ad hoc mode. Mobile ad hoc network (MANET). Multi-. Mobile Ad Hoc Networks (MANET). □ Host movement frequent. □ Topology change frequent. □ No cellular infrastructure. Multihop wireless links. □ Data must. Abstract—The wireless ad hoc networks consist of a collection of wireless nodes, that communicate over a common wireless medium. The nodes communicate.
Furthermore, In other words, Wi-Fi P2P does not need a centralized fixed physical infrastructure, and any device with Wi-Fi Direct enabled can participate in the negotiation.
Wi-Fi Direct or P2P specification is still at an early stage, and the many researchers have started implementing the technology. The proposed social networking protocol and implementation, OffAT, provides social applications including interests similarity and communication between similar users that has been built using Wi-Fi Direct in the commercially available devices. Architecture and Implementation The main components of the proposed mechanism are device discovery, interest-based social network, and intergroup communication.
Device Discovery Wi-Fi Direct devices discover each other using device discovery, wherein a P2P device selects a listen channel and alternates between the search state and listen state. The time for each state is allocated randomly between ms and ms but can be configured. Some researchers have used MAC ID as the device ID in the discovery process or some confidential ID that limits to connect with only a specified user [ 19 ] or using an Internet connection [ 20 , 21 ].
For example, MobiClique [ 22 ] used Bluetooth for device discovery to locate nearby users and a central server for matching the user profiles. Profile matching at a central server is only feasible in some cases due to the additional requirement of the server or infrastructure. The proposed method in this paper provides the mechanism and user interface to configure device ID as user name user interests.
This paper proposes an implementation of changing device ID to user name user interests so that interests can be broadcasted in the nearby region. The broadcasted interests can be representative keywords to be used as the first layer to filter users before actual connection. Using device ID to match user interests helps to reduce network overhead of establishing a social network of users who are not similar to each other and likely to not involve in social applications.
The below code explains the methodology used to extract user ID and interests in and set the device ID as user name and interests in in Java Algorithm 1. Algorithm 1 Figure 1 displays a user interface to configure device ID. Interests are automatically separated in the backend as a list of keywords based on space or comma operator as shown in the code. Modifying device ID to interests solves the following purposes: 1 All user devices can access interests of other users without any centralized infrastructure 2 Device can compute interests similarity and can decide whether to connect with other users or not 3 Computed similarity can also be used to accept or reject any incoming connection request 4 Reduces network overhead due to exchanging profiles Figure 1: User interface to configure device ID.
A device can have two statuses such as available or connected. A connected device can either be a group owner or an existing group member. Figure 2 shows the device discovery phase and displays the device status as available. Figure 2: Device ID displaying user name user interests in the discovery phase with status as available.
Profile Matching The profile matching is the core of social networking, especially location-based social networking. Figure 3 a displays a user device with device ID as user name interests as available along with nearby available devices, and Figure 3 b displays a user connected with user2. The discovery process can be manually started by clicking the hand icon available below user name and interests in case no user is found. The OffAT scans interests of nearby users and computes profile similarity based on matched keywords.
The option to send a request to a neighboring user, preferably a user with high profile similarity, is displayed along the right side of each user. The list of users can quickly be scrolled to see all users if the number of users is high.
Once the other user accepts the connection request, the status of both users will get connected as shown in Figure 3 b. The option to chat or disconnect and start the connection or discovery phase is displayed to the connected user as shown in Figure 3 b.
The cosine similarity of two user profiles varies between 0 and 1. Cosine similarity is 1 when the angle is 0 meaning the two profiles are exactly the same. In a vector space model [ 24 ], a user profile is represented by , where the elements are different keywords.
A union of all keywords of profiles is considered before computing cosine similarity. The weights represent the number of times a word appears in a browsing history or prior user action [ 6 , 24 ]. Gambhir et al. For the implementation of the mechanism and simplicity, the profile matching matches keywords to find the profile similarity percentage.
Social Communication Once the users are connected based on their profile, they can start chatting or sharing files. This phase may also be used to add more members to the group by sending a connection request to the server designated in negotiation when the request is sent to connect. OffAT also allows exchanging handwritten notes as shown in Figure 4.
Multihop communication can be facilitated by configuring a device as a client as well as a group owner where the device alternates roles based on time-sharing.
Figure 4: Exchange of text and handwritten messages in the airplane mode. Security Wireless networks are vulnerable to eavesdropping and intrinsically exposed to both active and passive security attacks.
This presents a challenge in the incorporation of key-based cryptographic mechanisms for ad hoc networks because there is no trusted authority to provide certification or a centralized key distributor. This implementation enables users to maintain privacy because the users can share user ID and limited interests without disclosing their e-mail ID or phone number unless they want to explicitly and are at liberty to decline linking requests invitations from other nearby users or disconnect.
Furthermore, the connection requests are automatically declined after 30 seconds when the request is not responded. This preventive mechanism further protects data integrity by authenticating sources and sequencing of messages.
The screenshots shown in this paper are from two devices Nexus 6P with one device in the airplane mode and the other using the telecommunication network and also connected to a Wi-Fi router in addition to participating in the ad hoc social network. During implementation and testing, it was observed that switching on Wi-Fi is required to participate in Wi-Fi Direct communication.
Therefore, there is a limitation in the airplane mode to manually switch on the Wi-Fi without even being connected to any centralized infrastructure. Although Android allows activating Wi-Fi programmatically, testing results with users indicated that this is not better since it sometimes delays the process of reconfiguring device ID.
Furthermore, asking users to manually switch on Wi-Fi provides the time that an app needs to modify the device ID with user ID and interests. The users are able to exchange text and handwritten notes among other nearby similar users without any centralized network infrastructure. Implementation results and feedback posted at Google Play Store indicated user preferences towards location-based social networking.
There are few suggestions by users to fix user name and interests, and they can be configured by Shared Preferences in the Android. Data Availability The research paper proposes a mobile app for location-based social networking. The app is available at Google Play Store, and link is available in the references. Conflicts of Interest The authors declare that they have no conflicts of interest. References Y. Wang, L. Wei, A. Vasilakos, and Q. Li, K. Bok, and J. Gambhir and N. View at Google Scholar B.
Guidi, M. Conti, and L. View at Google Scholar N. Aneja and S. Mao, J. Ma, Y. Jiang, and B. Eagle and A. Zhang, X. Ding, Z. Wan, M.
Gu, and X. Zhang, D. Zhang, H. Xiong, C.
Instead, systems could collectively use possible TVWS spectrum that is available in an open access manner. Furthermore, cognitive radio technologies have the potential to address interoperability issues of emergency communication systems, through two different means. Routing across regions with heterogeneous TVWS availability different radio communications systems on different frequencies or the cognitive radio system could be used to minimize mutual interference between two communication Taking into account the above scenario, spectrum systems deployed in the same operational crisis site.
The goal of routing in such networks is to provide of secondary users i.
Following this selecting the appropriate path between secondary users. Thus, introductory section, Section 2 elaborates on routing multi-hop connections must be set up between secondary users challenges in ad-hoc CR networks and the definition of the pairs with different spectrum availability and a new routing simulation scenario.
Section 3 presents the design of a novel protocol has to be designed and adopted, enabling for route routing protocol that enables for the proper data transition discovery capabilities, taking into account spectrum across secondary users with different TVWS availability, heterogeneity in different geographical locations.
Route while section 4 elaborates on the performance evaluation of quality issues have also to be investigated since the actual the proposed research approach. Finally, section 5 concludes topology of such multi-hop CR networks is highly influenced the paper by highlighting fields for future research. The transmission of secondary users in an ad-hoc CR Furthermore, route maintenance is a vital challenge network is based on spectrum opportunity.
Therefore, routing considering the above mentioned use-case scenario. The in such a network has to take into account the availability of unpredictable appearance of a primary user at a specific time spectrum in specific geographical locations at local level. In a general context, routing in a TVWS based ad- heterogeneous spectrum availability, even when the network hoc CR network constitutes a rather important but yet connectivity is intermittent or when an end-to-end path is unexplored problem, especially when a multi-hop network temporarily unavailable.
Figure 1 illustrates a use-case architecture is considered. The design of a new routing scenario, where primary users operate on specific channels in protocol is therefore required, towards overcoming challenges three geographical areas i.
Area A, B and C in Figure 1. TVWS in Figure 1. It has to be noted here that a In this context, Figure 2 depicts a simulation scenario, CCC does not exist between secondary users, which are where secondary users are scattered in three geographical located in neighbouring geographical areas i.
Area A, B and areas i. In such a case, secondary users that are located availability.
Secondary users located in the first geographical outside Areas A, B and C, i. In this use-case and , respectively.
These request message, including TVWS availability of nodes is nodes are enhanced with a coordination mechanism that sent by the source user to acquire a possible route up to the enables to determine routing paths between secondary users destination user. The destination user then chooses the optimum routing path, according to a number of performance metrics e.
It has to be noted here, that the evaluation of performance metrics is conducted, by each intermediate node during the routing path of the RREQ message. In the next step, destination user sends back a RREP route reply message to the source user that includes information regarding channel assignment so that each node along the route can adjust the channel allocation accordingly. Once this RREP is received by the source user, it initiates useful data transmission.
The source user initiates a flow i. The Geo-location node located in a neighbouring location. The intermediate database also provides to intermediate communication nodes, node is updated by Geo-location database about TVWS data regarding the maximum allowable transmission power availability of its neighbouring nodes and determines if it is that can be used so that no causing interference to primary capable or not to accommodate the incoming flow from source systems.
For this reason an initial study is required, in order to user. If this is possible, it then evaluates the performance compute the transmission power limitations of metrics, accommodates the incoming flow and finally communications nodes for each TVWS channel. Such an forwards the RREQ message to the next hop or to the investigation can be performed, by adopting the method, destination user. Destination user sends then back a users i.
This message contains data flows to corresponding destination secondary users i. The main accordingly. Once the source user receives the RREP, the challenge in such an ad-hoc CR network architecture is the routing path has been established and useful data transmission spectrum heterogeneity of the available TVWS between is initiated.
In such a case, accommodate the incoming flow i. In such a case, the intermediate node sends a RREP message to the source user, including redirection information. The proposed routing protocol implemented and evaluated under controlled simulation determines a route only when a source user wishes to send a conditions.
This routing protocol is based on the exchange of data flow to a destination user. Routes are maintained as long AODV-style messages  between secondary, including two as they are needed by the source user and the exploitation of major steps in the route discovery process i. This selection was made due to the free routing process. Furthermore, the proposed routing unpredictable availability of the TVWS that requires hop-by- protocol is a reactive one, creating and maintaining routes hop routing, by broadcasting discovery packets only when only if it is necessary, on a demand basis.
This value is set to a predefined for this route and expiration time of the flow. The number of value at the first transmission and increased during RREQ messages that a source user can send per second is retransmissions, which occur if no replies are received.
The formulation of mean queuing regarding the efficient performance of the proposed routing delay Dqueuing ,  is depicted below: protocol. In this context, a number of delay metrics , , 1 , , are evaluated, such as switching delay Dswitching , Additionally, the evaluation of Dswitching and Dbackoff ,  medium access delay Dbackoff and queuing delay Dqueuing.
Then, cumulative delay Switching delay occurs when a secondary user during the at an intermediate node i is based on them and is computed as routing path switches from one channel to another, while the follows: medium access delay, namely backoff delay, is based on the MAC access schemes used in a given frequency band.
Queuing Delay is based ND: on the output transmission capacity of a secondary user on a 3 given channel. More specifically, queuing delay represents the The simulation results that were obtained, provided the time needed for a data flow to wait in a queue until it can be routing paths for S1-D1, S2-D2 and S3-D3 communication processed.
Additionally, secondary user S2 wishes, at the same time discrete time is a step in the transition to transmit data flows to secondary user D2. In this case, of Markov model analysis. Each secondary node generates coordinator node 3 located between geographical areas B and packets at the beginning of every timeslot i. In case of targeted to secondary user D3. In such a case, data flows are unsuccessful transmission i.